1. Field of the Invention
The present invention relates to mechanical linkages for positioning an end effector such as a gripper.
2. Discussion of Background
An "end effector" is a tool or device designed for a particular function and operated from the end of a deploying or positioning handle. End effectors include gripping devices of all sorts, whether designed to grip one or more tools that perform an operation on a workpiece or to grip the workpiece itself and to move it or simply hold it while a second operation takes place with another tool.
Frequently, end effectors are designed so that they can be operated not only in line with a handle but also at an angle with respect to the handle. If the end effector can not be fixed at the particular angle needed, or if the angle varies from one operation to the next, the end effector and the handle may be interconnected by mechanical or electro-mechanical linkages so that the end effector can be positioned or rotated or turned as desired while the handle remains fixed. A linkage is composed of one or more links interconnected so as to cooperate with each other in the achievement of some motion of an end effector.
There are many examples of linkages that will allow flexibility in the coupling of the end effector to the handle, from robotic arms and servo-mechanical manipulators to socket wrenches. In particular, see Shackleford's gripper mechanism described in U.S. Pat. No. 4,243,257 and Greer, et al.'s material handling manipulator described in U.S. Pat. No. 2,765,930. Shackleford's device has an air cylinder that moves one of two links, the links pivotally interconnected, so that jaws operated from the links open and close. Greer's device is also a gripper, opening and closing by the manipulation of a hand grip separated from the gripper by a flexible hose so that the gripping operation can take place at large angles with respect to the hand grip.
In particular, there are linkage mechanisms that invert an object. See the mechanisms of Kitamura, et al. in U.S. Pat. No. 3,773,189, Misawa in U.S. Pat. No. 3,734,556, Youmans in U.S. Pat. No. 2,861,699, and Couser in U.S. Pat. No. 2,807,373. However, all of these rotate the object to invert it. It is sometimes necessary to grip an object from the end and turn it 180.degree. or more and hold it. There is a need for a mechanical linkage that deploys a gripper or other end effector and inverts it for application to a workpiece, especially a linkage that is compact so that it performs the inverting in a minimum of space.